The phone company nextfell has a monthly cellular plan where a customer pays a flat monthly fee and then a certain amount of money per minute used on the phone. if a customer uses 210 minutes, the monthly cost will be $108.5. if the customer uses 620 minutes, the monthly cost will be $252.

a) find an equation in the form
y
=
m
x
+
b
,
where
x
is the number of monthly minutes used and
y
is the total monthly of the nextfell plan.


y
=

b) use your equation to find the total monthly cost if 979 minutes are used.

if 979 minutes are used, the total cost will be
dollars.
get : video

1. y=0.35x+35

2. If 979 minutes are used, the total cost will be $377.65 dollars.

Step-by-step explanation:

1. Let $x be the flat monthly fee and $y be the amount of money paid per minute used on the phone.

If a customer uses 210 minutes, the monthly cost will be $108.5, thus

If the customer uses 620 minutes, the monthly cost will be $252, then

Subtract from the second equation the first one:

Substitute it into the first equation

We get the flat fee is $35 and the amount of money per minure used is $0.35. So, the equation of the function is

where x is the number of monthly minutes used and y is the total monthly of the NextFell plan.

2. When x=979, then

the system of inequalities is

step-by-step explanation:

step 1

find the equation of the dashed line

we have the points

(0,0) and (3,1)

the line passes through the origin, so, is a direct variation

find the slope

the equation of the dashed line is

the solution of the inequality a s the shaded area above the dashed line

therefore

the equation of the inequality a is

step 2

find the equation of the solid line

we have the points

(4,0) and (0,4)

find the slope

the equation of the solid line is

the solution of the inequality b s the shaded area below the solid line

therefore

the equation of the inequality b is

step 3

the system of inequalities is